The Prostate, Lung, Colon-rectum and Ovary Cancer Screening Trial (PLCO) is designed to determine in screenees aged 60-74 years at entry_whether: a. In females and male (1) screening with flexible sigmoidoscopy (60 cm sigmoidoscope) can reduce mortality from colo-rectal cancer; and, (2) screening with chest x-ray can reduce mortality from lung cancer. b. In males (1) screening with digital rectal examination plus serum prostate-specific antigen (PSA) can reduce mortality from prostate cancer; C. In females (1) screening with pelvic examination plus CA 125 and transvaginal ultrasound can reduce mortality from ovarian cancer; The Contractor shall establish a Laboratory and coordinate with the Screening Centers (SCs) and the Data Management and Coordinating Center (CC) for the PLCO Cancer Screening Trial and be responsible for: 1) conducting PSA assays, 2) conducting CA125 assays, 3) reporting results to SCs and CC, 4) quality control associated with the assays and with sample handling, 5) interaction with the SCs to ensure proper preparation, handling, and shipping of serum, 6) training and/or certification of individuals doing assays, 7) interaction with the assay manufacturers to ensure state-of-the-art practices, and 8) maintaining a skilled staff to carry out the work.